Action

In GitHub Actions, a packaged, reusable step that a workflow invokes by name and version — actions/checkout@v4, pnpm/action-setup@v4 — as opposed to a run: line, which is just shell

The unit of reuse, and the unit of supply chain. An action is somebody else’s code running with your repository checked out and your secrets in the environment, which is why pinning it to a version (better, a commit SHA) is not pedantry. The word is also used loosely for the whole product, so an action and Actions in the same sentence usually mean two different things.

A workflow run’s smallest billable unit of time; minutes are metered per repository and can be exhausted

Worth knowing because of how it fails: when minutes run out, checks go red without running. A red check then means did not run, not failed — so the gate has to move somewhere it can actually execute, and the run you can show becomes the local one on the pushed commit.